1. Field of the Invention
The invention relates to a device for transmitting and receiving radiation, disposed in a first medium for forming, from this first medium, an image of an object buried in a second medium.
2. Description of the Prior Art
The invention applies particularly to the case where it is desired to obtain non destructively an image of the bars and networks of metal bars embedded in concrete, for surveying, maintaining, repairing or reinforcing reinforced concrete works or buildings, for which for example no plan exists. In this case it is important to have an apparatus for determining the diameter, number and position of the bars in the concrete without having to make windows for laying bare the reinforcements locally, which is fastidious and sometimes dangerous. Naturally, the invention may apply to any other field in which it is useful to be able to form non destructively images of buried objects.
Devices of the above defined type are known which use a low frequency magnetic field and the disturbance thereof by any metal object disposed in its vicinity. These devices are known by a man skilled in the art under the name of "pachymeters" or "profometers". They are able to give indications about the position of the reinforcement the closest to the walls, and it is generally possible to determine, using charts, the diameter of a bar if the thickness of the concrete which surrounds it is known and conversely. However, in practice, the accuracy of these devices is such that they make it possible to detect the presence or absence of metal bars, in a certain volume, without it being really possible to know the number, depth and diameter thereof. Devices are also known based on the use of gamma rays or X rays, as in radiography or radioscopy systems in the medical field. However, these devices which use powerful sources for producing the radiation are very heavy and very expensive to use and require numerous and qualified staff. In addition, they are not without risks of irradiation. Moreover, on the negatives obtained, it is often impossible to interpret the image in the zones with high reinforcement density, and delicate to determine accurately the diameter of the bars whose position with respect to the source is unknown. Finally, these devices operate by transmission, which complicates the positioning and raises certain problems if the volume to be sounded is thick.
The present invention overcomes the above drawbacks by providing a device of the above defined type making possible accurate and rapid determination of the location and shape of the objects to be examined, working by reflection for easy positioning while being practically without danger for the operating staff, portable and of moderate cost.